Conventionally, various devices, methods, and the like, which determine existence or non-existence of the possibility of a collision with another vehicle have been suggested. For example, a collision prediction method described in the following is disclosed (refer to patent literature 1). More specifically, first, relative positions (relative distance, azimuth angle) and relative velocities of the object vehicle and a vehicle of one's own are obtained and stored, a parallel area is set which is parallel to an estimated moving direction of the object vehicle after elapse of a predetermined prediction time and in which the own-vehicle passes through, and an estimated existence region of an object vehicle is obtained based on a relative distance in a width direction from an edge of the object vehicle. Then, it is judged whether or not a prediction position of the object vehicle after the elapsing of the predetermined prediction time is within a predetermined threshold distance range from the own-vehicle (=collision prediction by using a danger range); and if the prediction position is within a threshold distance range, the possibility of a collision with the object vehicle is judged (=collision prediction by using lap possibility) based on a relative positional relationship between the parallel area and the estimated existence region.
[PATENT LITERATURE 1] Japanese Laid-Open Patent Publication No. 2007-279892